Praxis Core Academic Skills for Educators: Mathematics (5733)Statistics and ProbabilityMedium
A researcher is conducting an experiment where they flip a fair coin three times. What is the probability of getting exactly two heads in three flips?
- A1/2
- B3/8
- C1/4
- D1/8
Show answer & explanationAnswer & explanation
Correct answer: B. 3/8
The possible outcomes for three coin flips are HHH, HHT, HTH, THH, HTT, THT, TTH, TTT. There are 8 total outcomes. The outcomes with exactly two heads are HHT, HTH, THH. There are 3 such outcomes. So the probability is 3/8.
Why the other options are wrong
- A. This is the probability of getting at least one head or at least one tail.
- C. This is the probability of getting exactly one head or exactly one tail.
- D. This is the probability of getting all heads or all tails.
Basic Probability (Multiple Events)
The likelihood of a specific outcome occurring when there are multiple independent events.
- List all possible outcomes (sample space).
- Count favorable outcomes.
- Probability = (Favorable Outcomes) / (Total Outcomes).
Memory trick: Multiple events: list all paths, count the good ones.